Embodiments of the invention relate generally to devices and methods to break current, and in particular, to direct current (DC) circuit breakers applied in high-voltage direct current (HVDC) systems, medium-voltage direct current (MVDC) power transmission or distribution systems, or the like.
In recent years, the interest in HVDC or MVDC systems has been revived. In those HVDC or MVDC systems, DC circuit breakers are necessary to make the HVDC or MVDC systems more flexible and reliable for many applications such as multi-terminal HVDC grids, MVDC power distribution for subsea electrification, and marine MVDC power transmission and so on. The DC circuit breakers need to be developed and validated at full scale to operate a multi-terminal HVDC or MVDC grid protection for fast interruption time and low loss.
Existing mechanical DC circuit breakers are capable of interrupting HVDC or MVDC currents within several tens of milliseconds, but are too slow to fulfill the requirements of reliable HVDC or MVDC grids. For fulfilling the high speed requirements, several approaches have been investigated. For example, a DC circuit breaker consists of silicon insulated gate bipolar transistors (IGBTs), which are controlled to interrupt HVDC or MVDC currents within a few milliseconds. However, the traditional silicon IGBTs may consume lots of energy during the energy transmission process, which decreases efficiency. Furthermore, due to the silicon IGBTs generating a lot of heat, heat sinks need to be arranged on the silicon IGBTs. This requires additional space and increases the weight of the HVDC or MVDC grids, which in turn reduces their power density and performance.
For these and other reasons, there is a need for providing a new DC circuit breaker at least having capabilities of low conduction loss and faster switching speed.